Project Summary Characterization of primary human immune responses to infection or vaccination often relies on surveying peripheral lymphocytes, as access to the sites where primary responses occur, such as the draining lymph nodes (LN), are not readily accessible due to anatomical location and ethical considerations. Thus, the majority of studies examining human B cell activation and plasma cell differentiation are performed in vitro under normoxic tissue culture conditions. However, B cells are activated, differentiate, within the low oxygen germinal center of the lymph node, and subsequently migrate from one anatomical compartment to another, where they encounter differing compartmental oxygen levels, ranging from 1-5% in the lymph node to 5-13% in the peripheral blood. The effects that oxygen levels have on B cells during an active immune response, in particular migration, is unknown. We hypothesize that oxygen tension is a previously unrecognized B cell regulatory switch, altering chemokine receptor signaling and controlling B cell migration. To test this hypothesis we propose the following specific Aims. Aim 1: Define and model the transcriptome and proteome pathways responsible for O2 dependent functional changes in B cell migratory capacity. Aim 2: Model the overlapping transcriptome and proteome pathways responsible for calcineurin perturbation of the HIF-1? molecular switch in human B cells. Aim 3: To assess the in vivo impact HIF-1? stabilization has on vaccine efficacy in a mouse model of immune suppression. The proposed work is intended to fill a critical gap in our understanding of human B cell responses, specifically the quantitative effects differing oxygen levels have on B cells migration.